1 files changed, 71 insertions, 0 deletions
diff --git a/rust/crates/graphics/src/stroke.rs b/rust/crates/graphics/src/stroke.rs
new file mode 100644
index 00000000..4f2b6f31
--- /dev/null
+++ b/rust/crates/graphics/src/stroke.rs
@@ -0,0 +1,71 @@
+use tiny_skia::{BlendMode, Color, FillRule, Paint, Path, Pixmap, PixmapPaint, Stroke, Transform};
+
+use crate::definitions::StrokeAlign;
+
+pub fn apply_aligned_stroke(
+    pixmap: &mut Pixmap,
+    path: &Path,
+    stroke_width: f64,
+    stroke_align: StrokeAlign,
+    stroke_color: Color,
+) {
+    if stroke_width <= 0.0 {
+        return;
+    }
+
+    match stroke_align {
+        StrokeAlign::Inside => {
+            let Some(mut stroke_pixmap) = Pixmap::new(pixmap.width(), pixmap.height()) else {
+                return;
+            };
+            stroke_path(&mut stroke_pixmap, path, stroke_width * 2.0, stroke_color);
+            erase_outside(&mut stroke_pixmap, path, BlendMode::DestinationIn);
+            composite(pixmap, &stroke_pixmap);
+        }
+        StrokeAlign::Outside => {
+            let Some(mut stroke_pixmap) = Pixmap::new(pixmap.width(), pixmap.height()) else {
+                return;
+            };
+            stroke_path(&mut stroke_pixmap, path, stroke_width * 2.0, stroke_color);
+            erase_outside(&mut stroke_pixmap, path, BlendMode::DestinationOut);
+            composite(pixmap, &stroke_pixmap);
+        }
+        StrokeAlign::Center => {
+            stroke_path(pixmap, path, stroke_width, stroke_color);
+        }
+    }
+}
+
+fn stroke_path(pixmap: &mut Pixmap, path: &Path, width: f64, color: Color) {
+    let paint = Paint {
+        shader: tiny_skia::Shader::SolidColor(color),
+        anti_alias: true,
+        ..Paint::default()
+    };
+    let stroke = Stroke {
+        width: width as f32,
+        ..Stroke::default()
+    };
+    pixmap.stroke_path(path, &paint, &stroke, Transform::default(), None);
+}
+
+fn erase_outside(pixmap: &mut Pixmap, path: &Path, blend_mode: BlendMode) {
+    let paint = Paint {
+        shader: tiny_skia::Shader::SolidColor(Color::BLACK),
+        anti_alias: true,
+        blend_mode,
+        ..Paint::default()
+    };
+    pixmap.fill_path(path, &paint, FillRule::Winding, Transform::default(), None);
+}
+
+fn composite(target: &mut Pixmap, source: &Pixmap) {
+    target.draw_pixmap(
+        0,
+        0,
+        source.as_ref(),
+        &PixmapPaint::default(),
+        Transform::default(),
+        None,
+    );
+}